Usually, a check for conditions in a vehicle such as a tire air pressure etc. is an essential operation for running safety of vehicle. However, a manual check is a troublesome task, then a vehicle monitoring system for automatically monitoring conditions in a vehicle such as the tire air pressure etc. has been developed and also entered into an actual operation in a combination vehicle (hereinafter, a tow vehicle is referred to as “tractor”, and a towed vehicle as “trailer”).
Conventionally, with regard to such a vehicle monitoring system, for example, a system is proposed (e.g. Patent Document 1) in which a sensor unit (detecting device) for detecting a tire pressure and temperature of each tire of a tractor and trailer sends a wireless signal directly or through a transponder in the trailer to a cab unit (transponder) in the tractor, and the cab unit which receives information of the tire pressure and temperature displays the received information on a display (display unit) to inform an operator of warnings and the like. Also, a system is proposed (e.g. Patent Document 2) in which a tag (detecting device) formed by a combination of a responder beacon, pressure sensor and the like and provided for each of tires measures and transmits a RF (Radio Frequency) signal having its measurement results, then a monitor provided adjacent to each of the tires receives the RF signal, each of monitors is connected to a computer (transponder) provided in a vehicle through a data bus, and the computer (transponder) translates the RF signal transmitted from the tag of each tire to send information to a central display (display unit).
However, when the trailer towed by the tractor is replaced, if identification information of a plurality of detecting devices provided in a new trailer is not registered, the vehicle monitoring system disclosed in Patent Document 1 or 2 would not identify each of the detecting devices provided in the trailer, therefore the display provided in the tractor may not identify and display information transmitted from each of the detecting devices.
In order to address this problem, for example a system is provided (e.g. Patent Document 3) in that when the trailer towed by the tractor is replaced, environmental data is re-configured by connecting an electric key to a central unit (transponder) in the tractor, which key stores the environmental data including the identification information and the like of each of modules (detecting device) in the trailer.
Patent Document 1: National Publication of International Patent Application No. 2002-516399
Patent Document 2: National Publication of International Patent Application No. 2003-509260
Patent Document 3: Japanese Patent Publication No. H6-255436